1. Field of the Invention
The present invention relates generally to wheels and casters, and it relates particularly to low profile, low friction wheels and casters, and load moving devices.
2. Description of the Prior Art
The classic type of furniture caster is a wheel rotating on a horizontal axle mounted on a fork or yoke swivel-mounted forwardly of the wheel axle to achieve caster action. This type of caster has disadvantages of the highest possible profile with consequent instability, unsightliness both from the high profile and from the visible axle mounting, and a narrow footprint. The "footprint" is considered herein to mean that area of caster or other load-bearing wheel or wheels which engages the terrain. The narrow footprint of the classic exposed horizontal axle-type caster has a steep tangential relationship to the terrain such that it indents deeply into carpeting, leaving unsightly depressions, is difficult to set into motion, and continues to be difficult to move even after having been set into motion. Examples of this classic horizontal axle-type caster are seen in U.S. Pat. Nos. 3,718,942 to Arenson, 3,818,541 to Daniels, and U.S. Pat. No. 4,219,903 to Black. The Black patent discloses a pair of ball bearing races for improved freedom of the caster swivel action, but this creates an undesirably higher profile.
In order to conceal unsightly caster wheel mountings, the classic fork or yoke-type caster wheel axle mounting has for the most part been superseded by an inclined single axle upon which the caster wheel is cantilevered in laterally offset relationship to the general longitudinal axis of the caster, the axle and its mounting to the body of the caster being generally concealed by the caster wheel. This inclined, cantilever-type single axle caster wheel mounting has the inherent disadvantage of torsional stress of the wheel against the axle and of the axle against its mounting, which generally requires an undesirably long axle and resulting undesirably high profile. Examples of such cantilevered single axle arrangements are seen in U.S. Pat. Nos. 3,060,488 to Skupas et al, and 4,161,803 to Propst.
In order to relieve the inherent frictional binding stress of cantilevered single axle caster wheels, various rollable bearings have been adopted wherein a rollable bearing wheel or ball bearings support the caster wheel above the footprint region. The presence of such rollable bearings inevitably results in a relatively high caster profile. Examples of devices of this type are seen in U.S. Pat. Nos. 2,810,151 to Lapham, 3,928,888 also to Lapham, 4,034,436 to Ginder, 4,037,292 to Lapham, and 4,327,460 to Wolff.
All of these cantilevered, single inclined axle casters have the same disadvantages as the classic exposed horizontal axle casters of an undesirably high profile, and a narrow footprint having a steep tangential relationship to the terrain which tends to indent deeply in carpeting, leaving unsightly depressions and offering undesirable resistance to movement out of depressions and continued movement through carpeting.
Applicants are not aware of any prior art single axle caster which is not of cantilever construction and does not require some sort of rollable bearing means to relieve axle stresses.
In addition to the aforesaid deficiencies in prior art casters, applicants are not aware of any prior art caster in which the supporting body of the caster has a contoured glide surface which leads down to the caster wheel footprint region so as to additionally minimize indentation of the caster into carpeting and corresponding facilitation of movement through carpeting or over irregular surfaces.
Support wheels for movable loads which are not caster mounted have, in general, the same basic disadvantages as caster wheels, of having an undesirably high profile and a narrow footprint having a steep tangential relationship to the terrain.